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 Post subject: looking to try something different.
PostPosted: Wed Jul 10, 2019 9:40 am 


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Joined: 10 Jul 2019
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not sure if anyone else had seen any of these before, but i was thinking about DIY building an arcade cabinet and using a parabolic mirror to upscale the screen size. now of course theres that time traveler 3d hologram game cabinet but thats not all you can do with a parabolic mirror. using a more ramp like mirror rather than a half dish you can magnify the screen to be projected onto a parascoped mirror. now not sure how common this tactic was or howcrare such cabinets were but i do know they did exist because ive played them before. anyway the point here is im more wondering what CRT would be best to use for this type of cabinet. on size of the crt monitor i was thinking about getting a smaller tv like a 9 or 13 inch screen and upscaling it to a 20 inch projection. any advice?


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 Post subject: Re: looking to try something different.
PostPosted: Wed Jul 10, 2019 11:33 pm 


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Fascinating project, though from where i sit knowing nothing about fabrication of optics or what's available it sounds like a lot of work.

One thing to consider would be image brightness. A 9" CRT TV was designed for direct viewing, and even with a near-perfect mirror blowing up that image you're going to decrease brightness per unit by the factor of magnification. You'll also get a more grainy image, as consumer CRT's pretty much all used the same dot/stripe pitch, regardless of 9", 13", 19", 29" etc. So a 29" tube has a way higher TVL or image clarity than a 9" tube, everything else being equal.

One fix to the first problem might be something like an older arcade monitor from Nanao, say the Sega MC-2000-S with it's original tube (can't remember the NA variants but the service manual will say. Mine has a Mitsubishi but i'm in Aus). Those were designed to be overdriven slightly, so you can get a really bright image out of them.

There are ways to overdrive a consumer CRT, but they generally involve bypassing the feedback circuits on the beam current, which also messes with the x-ray protection circuit. Injecting your own amplified RGB direct to the neckboard is one way to do this - it's probably ok to do that medically speaking if you maintain an image no brighter than the TV could normally go, but if you boost the brightness or contrast you're upping the ionising radiation geometrically. Then again, in this case it'll be firing at the mirror, not at you, and that's going to be a big difference.


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 Post subject: Re: looking to try something different.
PostPosted: Wed Jul 10, 2019 11:58 pm 


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Location: Australia
Thought about using a beam scope?

https://www.gumtree.com.au/s-ad/charles ... 1216532462


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 Post subject: Re: looking to try something different.
PostPosted: Thu Jul 11, 2019 6:10 am 


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Syntax wrote:


Or even a small projector, i guess. Then again, even a small CRT projector isn't small or simple.


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 Post subject: Re: looking to try something different.
PostPosted: Thu Jul 11, 2019 8:50 am 


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buttersoft wrote:
Fascinating project, though from where i sit knowing nothing about fabrication of optics or what's available it sounds like a lot of work.

One thing to consider would be image brightness. A 9" CRT TV was designed for direct viewing, and even with a near-perfect mirror blowing up that image you're going to decrease brightness per unit by the factor of magnification. You'll also get a more grainy image, as consumer CRT's pretty much all used the same dot/stripe pitch, regardless of 9", 13", 19", 29" etc. So a 29" tube has a way higher TVL or image clarity than a 9" tube, everything else being equal.

One fix to the first problem might be something like an older arcade monitor from Nanao, say the Sega MC-2000-S with it's original tube (can't remember the NA variants but the service manual will say. Mine has a Mitsubishi but i'm in Aus). Those were designed to be overdriven slightly, so you can get a really bright image out of them.

There are ways to overdrive a consumer CRT, but they generally involve bypassing the feedback circuits on the beam current, which also messes with the x-ray protection circuit. Injecting your own amplified RGB direct to the neckboard is one way to do this - it's probably ok to do that medically speaking if you maintain an image no brighter than the TV could normally go, but if you boost the brightness or contrast you're upping the ionising radiation geometrically. Then again, in this case it'll be firing at the mirror, not at you, and that's going to be a big difference.


brightness loss wont be too much of a problem, ill simply boost the tvs brightness gamma and contrast using the TVs own menu settings, the resulting loss due to short travel distance should only be enough to make the boosted gamma's off black greys look more like true black.

far as optics im going to try uaing mylar first if that dsnt work ill use the HS chem lab trick of using silver nitrate to make a custom mirror. the resolution loss is a concern which is why i was thinking using more of a 13-19 inch tv but if there are better quality smaller tvs like idk a production monitor vs a consumer tv ild be interested in those on the below 13 inch models.


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 Post subject: Re: looking to try something different.
PostPosted: Thu Jul 11, 2019 6:27 pm 


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Location: n/america
How are you going to do the modelling to figure out the size and shape of the mirror? Do you have a simulation program which will help you dial in the specs, or are you just planning on doing all the math by hand?


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 Post subject: Re: looking to try something different.
PostPosted: Fri Jul 12, 2019 4:10 am 


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darth.brando wrote:
if there are better quality smaller tvs like idk a production monitor vs a consumer tv ild be interested in those on the below 13 inch models.


Yeah, the 8"/9"/10" models like the PVM-8044 or 8045 and the Ikegami TM10-17R or RA are about 450TVL, and that's higher than a consumer 19" model. Not to sound negative, I still reckon you'll be struggling with brightness issues. Still, i'm not an expert and it's not my project :)


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 Post subject: Re: looking to try something different.
PostPosted: Fri Jul 12, 2019 8:28 pm 


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vol.2 wrote:
How are you going to do the modelling to figure out the size and shape of the mirror? Do you have a simulation program which will help you dial in the specs, or are you just planning on doing all the math by hand?


ill ne doing the calcs in blender. ive already done the rough calculations to figure out relative scale sizes curves and distances. one added advantage to blender is that it also allows for accurate volumetric light measurement and emissions.


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